Template Injection

Executive Summary:

This report addresses a significant security vulnerability known as Template Injection within our application. Template Injection occurs when user-controlled input is improperly processed and embedded within templates, leading to the execution of arbitrary code or injection of malicious content. This report aims to detail the vulnerability, its potential impact on our systems and users, and actionable recommendations for mitigation.

Description of the Vulnerability:

Template Injection vulnerabilities arise when user-supplied data, such as template variables or expressions, is directly embedded within templates without proper validation or sanitization. Attackers can exploit these vulnerabilities by injecting template-specific syntax or commands, potentially leading to arbitrary code execution, server-side request forgery (SSRF), or cross-site scripting (XSS) attacks. Common examples include injecting template tags, expressions, or functions into template engines or markup languages used to generate dynamic content.


The impact of Template Injection vulnerabilities can be severe, leading to various security risks including remote code execution, data leakage, or compromise of sensitive information. Attackers can exploit these vulnerabilities to execute arbitrary code within the server's environment, access sensitive data, or perform unauthorized actions on behalf of compromised users, potentially leading to financial loss, reputational damage, or legal consequences.


The likelihood of exploitation depends on various factors including the visibility of user-controlled input within templates, the effectiveness of input validation and sanitization mechanisms, and the attacker's knowledge of template syntax and injection techniques. However, given the prevalence of Template Injection vulnerabilities in web applications and the potential impact on system security and user privacy, the risk associated with this vulnerability is significant if not properly mitigated.

Steps to Reproduce:

  1. Identify templates or markup languages used within the application to generate dynamic content.
  2. Submit user-controlled input containing template-specific syntax or commands via form fields, URL parameters, or other input mechanisms.
  3. Analyze the application's response and observe if the injected content is rendered within the generated templates.
  4. Determine if the injected content results in unexpected behavior, execution of arbitrary code, or injection of malicious content.

Recommendations for Developers:

  1. Implement Strict Input Sanitization: Implement strict input validation and sanitization mechanisms to ensure that user-controlled input is properly sanitized before being embedded within templates.
  2. Use Safe Template Engines: Utilize template engines or markup languages that provide built-in protections against Template Injection vulnerabilities, such as automatic escaping of user input.


Addressing Template Injection vulnerabilities is critical to protecting against remote code execution, data leakage, and compromise of sensitive information within our application. By implementing strict input sanitization mechanisms and using safe template engines, we can mitigate the risks associated with Template Injection vulnerabilities and enhance the overall security posture of our systems.